The invention relates to an apparatus for monitoring a change in the status of binary information from a multiplicity of input points.
A chemical, textile, petroleum, electrical or gas industry involves processes and systems which contains a multiplicity of sites to be monitored. In these processes, an alarm signal from any site is fed to a centralized monitoring system. This renders it difficult to determine which alarm has operated if one of the alarms restores a normal condition immediately after it once operated. Such a difficulty can be avoided by an alarm unit which provides a self-holding function in response to an alarm signal once generated. However, in this instance, the alarm unit continues to operate even after the signal restores its normal level. It is desirable that an indication of the alarm be automatically interrupted upon restoring to a normal level, and therefore the self-holding feature is not desirable. In a system which is susceptible to a chain reaction in that the occurrence of a single abnormal condition induces additional abnormalities, it will be useful for the remedy, re-starting or the analysis of an accident to know the sequence in which the alarm signals are generated, or more specifically, the sequence in which the abnormalities occur and propagate as well as the time interval between successive abnormalities. During the starting and shutting down procedure of the process, it is necessary to perform sequential operations in a given order, and a wrong procedure may result in an accident particularly during the starting and shutting down. Under such situation, a record of the procedure employed will facilitate locating a wrong operation, enabling an immediate action to be taken under certain circumstances. While a conventional process control has used a record of information concerning a multiplicity of process variables, there has been no system for recording the presence or absence of the abnormality of such variables. This may be explained by the fact that such abnormality should not occur frequently, and actually occurs only rarely. For this reason, it is not favorable in respect of the process economy that the recorder be normally maintained operative.
It is an object of the invention to provide an apparatus for monitoring a change in the status of a multiplicity of input points, occurring in the form of a binary information, which records any change occurred only when it occurs, permits an effective use of a recording medium and provides a legible record output.
It is another object of the invention to provide an apparatus for monitoring a change in a multiplicity of inputs which permits a high speed survey of the varying status of a multiplicity of input points.
It is a further object of the invention to provide an apparatus for monitoring a change in a multiplicity of inputs which achieves an accurate record of the sequence in which a change in the status of a multiplicity of input points occurs.
It is an additional object of the invention to provide an apparatus for monitoring a change in a multiplicity of inputs which produces a record which permits, at one glance, the recognition of characters, symbols or numerals indicative of the input points, the prevailing status of the input points as well as the time at which the record is made.
It is still another object of the invention to provide an apparatus for monitoring a change in a multiplicity of inputs which permits the form of a record to be established and modified in a simple and free manner.
It is a still further object of the invention to provide an apparatus for monitoring a change in a multiplicity of inputs which is simple in operation and maintenance, and which can be handled by unskilled persons.